Sunday, June 12, 2011

White-faced Ibis and ? @ Pt. Mouillee - 11 Jun 2011

A pair of Plegadis sp. ibis highlighted today's trip to Pt. Mouillee SGA, Monroe Co., MI.  One bird is an obvious White-faced Ibis (P. chihi) while the second shows traits of an intermediate or Glossy X White-faced hybrid.  Discussion to follow.

A bit of late start this morning had me arriving at the Mouillee Creek entrance at just before 8 am.  A leisurely ride along the Middle Causeway brought me to the Lautenschager Unit, which I hadn't visited all spring.  The water level was high, so there were no mudflats for possible shorebirds.  The place was quiet except for a pair of birds that flushed from the shoreline far ahead of me.  I thought nothing of them until they banked east and started flying across the field in front of me.  Dark bodies and long necks confused me until I put the binocs on them and realized that they were dark ibises!  I fired off a few frames to capture their silhouettes.  They flew across the Bloody Run and Long Pond Units and disappeared into the Vermet Unit (near the eagle nest), so I suspected that I might run into them again near the southeast corner of the Vermet Unit.

I continued along the Middle Causeway to the junction of Long Pond, Humphries and Vermet Units where I decided to walk the bike for fear of spooking any shorebirds that might be in the mudflats east of the sunflower field.  Up ahead I could see a Snowy Egret  among a flock of Mallard and several Canada Geese (w/ goslings). I also saw a van along the east dike that I suspected belonged to Adam Byrne, so I called him, only to find out that he and Scott Terry had seen the ibis earlier this morning in the same area.  They ID'd the birds as White-faced Ibis and a possible hybrid.  I told him that the birds were in the area, having watched them fly this way from the Lautenschager Unit.  It wasn't until I hung up the the phone and walked another 30 yds. that I saw two dark forms near the egret that I knew immediately must be the ibis.

As I approached the birds slowly from the path the Mallards flushed, taking all the birds with them.  The Snowy Egret disappeared northward over the Vermet Unit while the two ibis took off north, then circled back around and returned toward the vicinity.  They must've seen me and continued off to the northwest, but not before I could get a few flight shots from a distance of 50 yds. or so.  The obvious White-faced Ibis (right) appears to be missing its P2 primary feather (assuming it has 11 primaries).

While I watched them disappear over the Vermet Unit I heard the distinct "kick-kiddick-kiddick" of a Virginia Rail calling loudly from the phragmites to my right.  I decided to walk to the edge of the phragmites and see if it would respond to the vocal sounds from the Sibley app on my Android.  I was surprised when I saw a tiny dark body dart out from the phragmites to my left.  Thinking it might be rat I crouched down into the grass and crept closer.  The rail sounded closer and suddenly appeared just a few feet away.  I was unable to photograph it with tall grass between me and the bird.  But it darted out and stopped long enough for a poor photo that I converted (in Photoshop) to a dry-brush watercolor.  It was neat to sit just a few feet from the bird as it grunted away at its unknown, territorial rival.  Before returning to the path I listened to the 'cuk-cuk-cuk' of a Least Bittern nearby, and to chatter that sounded like chicks from an invisible nest.

Returning to the path I found the two ibis feeding at the edge of the planted field along the south edge of the Vermet Unit.  I spent the next several minutes digiscoping the pair from about 60 yds. before Adam and Scott arrived.

One bird appeared to be a distinct, alternate (breeding) White-faced Ibis, complete with red eye and white facial feathers surrounding a pink loral skin that surrounds the eyes.  Bill is gray, legs are pink, and neck and head feathers show no evidence of brown or white flecks that would suggest a non-breeding adult or juvenile bird.  Kaufman (2011) describes the simple alternate plumage strategy of White-faced Ibis in his new book.

The second bird is a bit more curious and worthy of closer inspection.  It also appears to be an adult in alternate plumage as evidenced by the scarlet/brown head and neck.  A non-breeding adult would show paler brown feathering with white fleks. Its bill is gray, and legs show a pinkish coloration that also suggest White-faced Ibis.  Legs appeared slightly darker than the former bird, but note that leg coloration is variable in Plegadis ibis and not a good indicator for species separation.  
Immediately evident is the lack of white feathering surrounding a pink loral skin that covers the face.  The eyes on this bird also appeared darker than expected for an alternate-plumaged adult WFIB (not bright red).  Dark eyes are a trait of Glossy Ibis, so the evidence is here supporting a hybrid White-faced x Glossy Ibis.   And, while I fully agree with anyone suggesting that this bird is indeed a hybrid (and should stop here), I've done just enough research to ask a question or two:  Sibley (2000) described in his book a bright vs. drab adult, with this individual looking much like the drab adult.  Is it possible for a breeding-plumaged adult WFIB not to have a 'high-breeding' appearance? Can hormone deficiencies affect this bird enough to make it appear as a hybrid?  This bird shows evidence of slight white feathering (initiating?) along the forehead.

On a Glossy Ibis the loral skin tends to be bluer/grayer, and any white bordering the eye tends to disappear behind the eye.  On this bird the loral skin has a pink coloration and there is evidence of skin behind the eye, but I don't know if this is significant of either species.   Although dark, the eyes do show evidence of red.  Are they red enough?  Of course, it probably doesn't matter whether this bird is a pure WFIB or a hybrid, but we can, at least, raise some questions for those more-experienced to address...  Arterburn and Grzybowski (2003) published an interesting article in American Birds regarding hybridization in Plegadis ibis.

I left the guys and headed out to Cell 3, where they had earlier seen 4 White-rumped Sandpipers along w/ Semipalmated Plovers and Sandpipers, and Dunlin.  My visit yielded only a dozen or so Dunlin and the Semi's far across the mudflats along the east side of Cell 3.  I only stayed a few minutes to scan the flats, and to scan the scan the Humphries Unit for Cattle Egrets (3 in the trees among numerous Black-crowned Night Herons).

From there a ride along the east shore of the Vermet Unit yielded only the usual Great Egrets, Tree Swallows, BCNH, Common Moorhens and American Coots.  I stopped along the North Causeway long enough to digiscope some near-shore Lesser Scaup among several Redhead ducks (nice to see this late in the spring).
Just before heading back along the west side of the Vermet Unit I took a few minutes to photograph fly-by Forster's Terns foraging/diving along the north shoreline.  They are gorgeous!

Heading back toward the car I decided to take a little side trip.  Behind the pump house a path leads due south along the west side of the Humphries Unit.  Never been along this route I decided to bike a ways to see if anything of interest would show up.  Warbling Vireos, Baltimore Orioles and more BCNH's were the only birds of interest.  I did stop long enough to grab a photo or two of a Dot-tailed Whiteface dragonfly that was flying about on the trail.

Back near the pump house I found this Indigo Bunting singing from a low branch long enough to digiscope from about 50'.  Its mate, a drab brown female finch, surprised me by responding to a simple 'pish'.

A Common Yellowthroat also made an appearance just long enough for a quick photo w/ the D300.

Returning to the car I decided to make a quick pass along Haagermann Rd to see if I could kick up a sparrow or two.  Bobolink and Eastern Meadowlarks could still be heard out in the radio tower field as I slowly cruised the dirt road.  But the 'dik-dik-di-di-di' of a Dickcissel (my 1st of the year) caught my attention.  The mostly-brown sparrow flew across the road in front of the car and landed atop the fence, where it sang w/ its back to me.  The gray nape and brown streaking on the back can be real confusing when trying to ID the bird from behind. 

It isn't until the bird turns around that you get to see (and appreciate) its real beauty!  I was able to digiscope the bird from about 40' for several minutes, using the scope at full-zoom and the camera at almost-full zoom to capture images up to 2000mm in equivalent focal lengths.

While driving back north along US-Turnpike Rd. I spotted a Cattle Egret foraging in the grass next to the pond at the corner of Roberts Rd. I pulled off to the side of the road and digiscoped the 'high-breeding' adult bird (red bill and feet) while it foraged in the grass. I put together this composite image showing how far back it bobs its head while walking!

Great morning!


Kaufman, Kenn, Kaufman Field Guide to Advanced Birding, 2011, Houghton Mifflin Harcourt, New York.

Sibley, David Allen, The Sibley Guide to Birds, National Audubon Society, 2000, Alfred A. Knopf, New York.

Arterburn, James W., and Grzybowski, Joseph A., Hybridization Between Glossy and White-faced Ibises, 2003, North American Birds, Vol. 57, No. 1, pp. 136-139.


Andy Dettling said...

Awsome pics. Another great day at the Mou.

Andy Dettling said...

Great pics. Another great day at the Mou.

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